Formose reaction
The formose reaction, discovered by
portmanteau
of formaldehyde and aldose.
Reaction and mechanism
The reaction is
aldose-ketose isomerizations. Intermediates are glycolaldehyde, glyceraldehyde, dihydroxyacetone, and tetrose sugars. In 1959, Breslow proposed a mechanism for the reaction, consisting of the following steps:[3]
The reaction exhibits an induction period, during which only the nonproductive
ribonucleic acid. The reaction conditions must be carefully controlled, otherwise the alkaline conditions will cause the aldoses to undergo the Cannizzaro reaction
.
The aldose-ketose isomerization steps are promoted by chelation to calcium. However, these steps have been shown to proceed through a
enediolate, as previously proposed.[5]
Significance
The formose reaction is of importance to the question of the
origin of life, as it leads from simple formaldehyde to complex sugars like ribose, a building block of RNA. In one experiment simulating early Earth conditions, pentoses formed from mixtures of formaldehyde, glyceraldehyde, and borate minerals such as colemanite (Ca2B6O115H2O) or kernite (Na2B4O7).[6] However, issues remain with both the thermodynamic and kinetic feasibility of binding pre-made sugars to a pre-made nucleobase, as well as a method to selectively employ ribose from the mixture. Both formaldehyde and glycolaldehyde have been observed spectroscopically in outer space, making the formose reaction of particular interest to the field of astrobiology
.
References
- ^ A. Boutlerow (1861) "Formation synthétique d'une substance sucrée" (Synthetic formation of a sugary substance), Comptes rendus ... 53: 145–147. Reprinted in German as: Butlerow, A. (1861), "Bildung einer zuckerartigen Substanz durch Synthese" (Formation of a sugar-like substance by synthesis), Justus Liebigs Annalen der Chemie, 120: 295–298.
- PMID 11058157.
- .
- S2CID 85029255.
- PMID 24575857.
- S2CID 5499115.